UNoxygenated blood enters theatrium on the right side of the heart. Unoxygenatedblood comes in fromthe top of the body through thesuperior vena cava. Unoxygenatedblood comes in from the lower body though the inferior vena cava.
While the unoxygenated blood is in theright atrium, thetricuspid valve is closed to keep the blood fromflowing down to the ventricle.
The atrium contracts and the tricuspid valve opens,forcing the blooddown into the ventricle.
The tricuspid valve closes again so that blood cannot move back upinto the atrium.
The ventriclecontracts. This forces theunoxygenatedblood throughthe pulmonary valve and intothe pulmonary arteries.
The right pulmonary artery takes theunoxygenated blood to the right lung. The left pulmonary artery takes theunoxygenated blood to the left lung. THE PULMONARY ARTERIES ARE THE ONLY ARTERIES THAT CARRY UNOXYGENEATED BLOOD.
In the lungs, the carbondioxide in theblood diffuses into the alveoli.The oxygen in the lungs diffuses into the blood. This is calledgas exchange. http://www.webmd.com/hw/health_guide_atoz/tp10237.asp
Oxygenated blood from the lungs enters the heart through the left atrium.The mitral valve isclosed to keep the blood from goinginto the ventricle.
Oxygenated blood from the right lungreturns to the heart through the right pulmonary vein. Oxygenated blood from the left lungreturns to the heart through the left pulmonary vein. THE PULMONARYVEINS ARE THE ONLY VEINS THAT CARRYOXYGENATED BLOOD.
The left atriumcontracts. This forces the oxygenated blood throughthe mitral valve into the right ventricle.
The mitralvalve closesagain. This keeps theoxygenatedblood frommoving backup into the atrium.
Oxygenatedblood is forced into the aortato be carried to the rest of the body.
Oxygenated blood is carried to allbody cells where oxygen diffusesinto the cells and carbon dioxide diffuses into the blood. Blood carrying carbon dioxidethen returns to the heart.
And thecycle begins again.
Blood Flow: Summary
Blood Vessels: Arteries, Veins, and CapillariesArteries and arterioles have alayer of smooth muscle tissuewhich allows them to contract(vasoconstrict) and expand(vasodilate), altering theirdiameter and thus blood flow. Walls of arteries and arterioles have many elastic fibers enabling them to withstand high pressures.
Artery and VeinArtery Vein Note the much thinner walls in veins.
Haemoglobin Chemical – protein Binds to oxygen to carry oxygen around the body. When oxygen is bound to it, it is called oxyhaemoglobin.
Types of CirculatorySystem
Circulatory SystemsFor larger or more active animals, some form ofmore efficient circulatory system is necessary forinternal transport.• Two types of circulatory system are found: Open Circulatory Systems Closed Circulatory Systems
Open Circulatory System• Hemolymph leaves the heart in short, branched arteries that open up into large spaces called sinuses.• Hemolymph percolates around organs, directly bathing the cells.• Hemolymph then returns to the heart directly or through short veins.
Open Circulatory System • Advantage - Exchange of materials is direct between the hemolymph and tissues. There is no diffusion barrier. • Disadvantage - Little fine control over distribution of the hemolymph to body regions. No mechanism for reducing flow to a specific part of an organ.
Open Circulatory System• Open circulatory systems tend to be found in more inactive animals.• Most molluscs have an open system, but the highly active cephalopods (squid and octopus) have evolved a closed system.• Insects have circumvented limitation of their open system by their tracheal system for oxygen supply.
Closed Circulatory System• The blood is contained within a completely closed system of vessels.• Vessels form a closed loop, usually with some sort of pumping organ like a heart or contractile vessels.• Vessels branch into smaller and smaller tubes that penetrate among the cells of tissues.
Closed Circulatory SystemAdvantages:• Fine-scale control over the distribution of blood to different body regions is possible.• Muscular walls of vessels can constrict and dilate to vary the amount of flow through specific vessels.• Blood pressures are fairly high and the circulation can be vigorous.
Human CirculatorySystemA Closed Circulatory System
How does this system work?pulmonary vein lungs pulmonary artery head & arms aorta main vein Right Left liver digestive system kidneys legs Circulatory System
Our circulatory system is a double circulatory system. This means it has two parts parts. Lungsthe right side of the left side of the system the system deals with deals with deoxygenated oxygenated blood. blood. Body cells